TU-decay measures genome-wide mRNA half-lives without transcription arrest. (A) Distribution of whole embryo mRNA half-lives based on uridine chase conditions (Uridine only) and uridine chase combined with actinomycin D to arrest transcription (Uridine + ActD). t1/2 = half-life. (B) Individual transcript decay curves based on the uridine-only and uridine + actD measurements. Chase times are plotted on the x-axis (0-hour = end of 1-hour pulse). Mean chase/pulse values are plotted at the 1-hour and 3-hour time points, and curves were fit using a single-order exponential decay equation. Error bars are standard deviation.